This invention relates in general to polymeric films, and in particular, to seamless polymeric films and to a process for preparing the films as belts for use in an electrophotographic imaging member. The polymeric films of the present invention comprise blends of polymers prepared by electrocodeposition.
Electrophoretic deposition of polymers in solution is a known process for obtaining polymeric films. Typically a dispersion of charged particles is deposited on a surface by application of a voltage or current in an electrodeposition bath. Polymer films obtained by the electrodeposition process may be used for a variety of purposes, such as for use in an electrophotographic imaging member.
A number of electrophotographic imaging members are known which comprise a photoconductive material deposited on a rigid conductive substrate. These imaging members require elaborate, highly sophisticated, and expensive equipment for fabrication. For example, imaging members have been prepared by vacuum depositing selenium alloys onto rigid aluminum substrates. Imaging members have also been prepared by coating rigid substrates with photoconductive particles dispersed in an organic film forming binder. Coating of rigid drum substrates also has been effected by various techniques such as spraying, dip coating, vacuum evaporation, and the like. Rigid drum imaging members, however, limit apparatus design flexibility, are less desirable for flash exposure, and are expensive.
Flexible imaging members are also known. Flexible organic imaging members may be manufactured by coating a web, and thereafter shearing the web into segments which are then formed into belts by welding opposite ends of the sheared web. The resulting welded seam on the imaging member, however, disrupts the continuity of the outer surface of the imaging member and therefore must be indexed so that it does not print out during an imaging cycle. Efficient stream feeding of paper and throughput are thus adversely affected because of the necessity to detect a seam within the length of each sheet of paper. The mechanical and optical devices required for indexing add to the complexity and the cost of copiers, duplicators, and printers, and reduce the flexibility of design. Welded belts are also less desirable for electrophotographic imaging systems because the seam forms a weak point in the belts and collects toner and paper debris during cleaning.
Accordingly, seamless belts suitable as substrates for electrophotographic or ionographic imaging members are particularly desirable. One method of obtaining seamless belts is by electrodeposition.
U.S. Pat. No. 3,676,308 to Brown discloses electrocodeposition of polyvinylidene chloride and copolymer particles with copper. Fine particles of organic resins derived from vinylidene chloride densely codeposit with copper when dispersed in aqueous acidic copper electroplating baths. Two-phase copper coatings having densely embedded resin particles are obtained.
U.S. Pat. No. 3,761,371 to Dickie et al discloses electrodeposition of various coating materials. Particulate elastomers may be mechanically mixed with an electrodepositable carrier resin and electrodeposited. The elastomer electrodeposits as a reaction product with a monomer or low molecular weight prepolymer that provides the reaction product with an ionizable surface functionality.
U.S. Pat. No. 3,798,143 to Rolles et al discloses an electrophoretic deposition of an acrylic interpolymer comprising methacrylate and an acrylic acid on an aluminum substrate from an aqueous colloidal dispersion. The coating is coalesced on the aluminum or anodized aluminum substrate by heating or by a coalescing agent.
U.S. Pat. No. 3,869,366 to Suzuki et al discloses a method of electrocoating which comprises immersing an electrically conductive metallic article in an aqueous electrode deposition bath containing a cationic binder resin and a non-ionic synthetic resin powder dispersed therein. The cationic binder resin is neutralized with an acid compound and the non-ionic synthetic resin powder in the deposition bath.
U.S. Pat. No. 3,920,532 to Hansen et al discloses a process for electrodeposition of a dispersion of finely divided substances in an apolar dispersing agent. The dispersion includes surface-active ion-forming substances which are soluble in a dispersing agent and are dissociable.
U.S. Pat. No. 4,425,467 discloses a method of making a non-aqueous emulsion from which a polymer can be electrodeposited. A mixture is prepared of about 50 to about 150 parts by weight of a non-aqueous organic, non-electrolyzable, non-solvent for the polymer with about 0.8 to about 1.2 parts by weight of a nitrogen-containing base which can be a tertiary amine, an imidazole, or mixture of a tertiary amine and an imidazole. To the mixture is added a solution of 1 part by weight of the polymer which can be a polyamic acid, a polyamide imide, a polyimide, a polyparabanic acid, a polysulfone, or a mixture of these polymers. The polymer is in a non-aqueous, organic, non-electrolyzable aprotic solvent such as N-methyl-2-pyrrolidone.
In addition, "An Electrically Conductive Plastic Composite Derived from Polypyrrole and Poly(vinyl Chloride)", M. De Paoli et al., Journal of Polymer Science, Vol. 23, pages 1687 to 1698 (1985), discloses a process for obtaining an electrically conductive plastic material by the electrochemical polymerization of pyrrole in a poly(vinyl chloride) matrix to form a composite wherein the polypyrrole is uniformly distributed in the poly(vinyl chloride) matrix. A film of poly(vinyl chloride) is cast on the surface of an electrode, and the coated electrode is used to generate polypyrrole in the pores of the matrix. Further "Conductive Composites from Poly(vinyl chloride) and Polypyrrole", M. De Paoli et al., J. Chem. Soc., Chem. Commun., pages 1015 and 1016 (1984), discloses a process that entails the electrochemical polymerization of pyrrole on a platinum electrode covered with film of poly(vinyl chloride) to produce a composite polymer film.
William W. Limburg, Santokh S. Badesha, and John S. Facci in "Seamless Conductive Substrate for Electrophotographic Application," Xerox Disclosure Journal, Vol. 14, No. 2 (1989) disclose a conductive substrate comprising an interpenetrating polymer domain network comprising an electrically conductive polypyrrole in a host polymer such as polyvinyl chloride. The interpenetrating network can be prepared by depositing the host polymer on a cylindrical metallic electrode by electrostatic powder or solvent spray processes, followed by immersing the host polymer and the conductive mandrel in a bath containing a solution of pyrrole in an electrolyte solution and anodically electropolymerizing the pyrrole to deposit conductive polypyrrole throughout the void areas of the host polymer. Alternatively, the pyrrole swelled host polymer can be contacted with diethyl selenite to cause the pyrrole to polymerize oxidatively to polypyrrole on contact. Further, an interpenetrating domain network of polypyrrole can be created by diffusing separated solutions of diethyl selenite and pyrrole in a swelling solvent into the host polymer from opposite sides of the film so that oxidative chemical polymerization of pyrrole occurs within the host polymer where the separated solutions intersect.
Although the above-described patents provide methods for electrodepositing various materials, there remains a need for an electrodeposition process which enables the preparation of polymeric compositions with superior mechanical and physical properties. In particular, seamless photoreceptor substrates which are flexible, tough, noncompliant and tear resistant are desirable. However, these substrate properties are difficult to obtain in a pure single component polymeric material. For example, photoreceptor substrate materials, such as polyamideimide, possess many superior mechanical properties except for tear and crack propagation. It is thus desirable to fabricate substrates in which the desired mechanical properties of a polymer may be tailored for individual applications.